This invention relates to magnetic tape cassettes. More particularly, it relates to elimination of the electrostatic charges which build up within the cassette when magnetic tape is transported from reel to reel within the cassette.
During operation of a magnetic tape cartridge static electricity is generated by rubbing of the tape over stationary tape guiding surfaces made of different materials than that of the tape itself. This static electric charge causes two major problems to the operation of the cartridge: (1) Due to differing electrical potentials between them and the tape, dust and debris are attracted to the tape surface. This results in interference with the tape's function by scratching it or causing interference between the tape coating and the recording or playback head resulting in lost or reduced signal transfer (drop-outs). (2) The electrical charges generated at the contact areas between the tape and the tape cartridge (such as tape guides) create an electrical potential and thereby cause an electrostatic attraction between the charged materials. This attraction between the tape and the stationary tape guides in the cartridge increases the friction already present to a degree which can result in failure of the tape to run smoothly.
The buildup of electrostatic charges during tape transport within cassettes is well known, and numerous techniques have been devised for discharging the static electricity. Typically, the prior art has provided for electrical connection between the substrate containing the static electric charges to ground such as by connection of the tape and/or cassette to the cassette player unit. Other arrangements have provided for electrically connecting both sides of the magnetic tape to cancel static electric charges. See European patent application No. 0074032, particularly FIG. 2, in which metal straps electrically connect stationary guides for both sides of a magnetic tape.